抄録
To draw a perspective, we have to draw many straight lines passing through a vanishing point. If the vanishing point exist outside of the drawing board, it is difficult to draw them without instrument. We devised a drafter useful in such a case. This drafter has two sliding guide ways by both sides of the drawing board. A slider A moves along the right guide way. Two sliders B and C move along the left guide way. The positions of slider A and B are determined by a straight bar which turns round a fixed point inside of the drawing board. The displacements of A and B are in the opposite direction and the ratio of these is constant. The sliders B and C are connected by pulleys and a belt, so their displacements are equal in length and opposite in direction. Then, the displacements of A and C are in the same direction and the ratio of these is constant. The elongation of the straight line connecting the sliders A and C passes through a fixed point outside of the darwing board. Therefore, we can draw many straight lines passing through a vanishing point outside of the drawing board.
